A conventional LED array is shown in FIGS. 1 and 2 wherein an LED chip 1 is mounted on either side (the top surface in this case) of a signal interconnection board 2, while (positive-) and (negative-) N-patterned power supply lines 11 and 12 for driving the LED chip (LED chips) are provided on the other side (the bottom surface in this case) of the signal interconnection board 2 to constitute the LED array. As the LED chip 1, either the one which has been prepared from a plurality of LEDs into a single chip, or a plurality of chips each of which has been prepared in the form of a single LED may be applied. In either case, an LED array is constituted on the top surface of the signal interconnection board 2. The patterned power supply lines 11 and 12 are prepared by a printed wiring operation wherein the P-patterned power supply line 11 and the N-patterned power supply line 12 are provided by a printed wiring manner, respectively. These patterned power supply lines 11 and 12 are connected to an external power supply through an interconnecting means.
It is to be noted that there has heretofore been no such LED array wherein a capacitor is provided between positive and negative power supply lines.
Meanwhile, power supply voltage for driving LED is applied between positive and negative power supply lines. In this case, voltage drop occurs due to rush current at a moment when the LED is turned on. For this reason when all the LEDs are turned on at the same time, lowering of light output and variations in light output among the respective LEDs arise. In order to prevent occurrences of such lowering of light output and such variations in light output, LEDs have been divided into a plurality of groups, and they have been sequentially turned on while accomplishing time shifts in every groups. Because of such sequential turn-on for LEDs, it was difficult to establish prompt operation for selecting turn-on or turn-off action for LED arrays.
Furthermore, since power supply lines are ones which have been patterned on a signal interconnection board, large amounts of current cannot be applied. Hence, current to be applied to respective LEDs are also restricted, so that high light output cannot be obtained.